I think one of the things that Lewis and Clark observed is the tameness of animals in the west. They're sort of constantly speaking in their journals of literally having to chase wolves out of their camps. And that also, I think, has to do with--lots of the animals they were seeing, particularly in eastern Montana, were not hunted very much. Whenever they were in the vicinity of Indian villages, for example, farther down the river, they had very different experiences with animals--deer that fled from their approach at considerable distances; buffalo that acted wary; wolves that didn't really come too close.
But predators, by and large, like wolves and bears, were usually not hunted very much by Indians. Wolves were very rarely hunted by Indians, in any case, and bears were sometimes hunted, but more or less in the same way that a Zulu warrior goes out and takes on a lion. It was to prove one's mettle as a warrior, and nothing like the later campaigns of extermination by stockmen against bears and wolves.
So those animals, I think, would've routinely been fairly tame. But that buffalo and deer and sheep, and so forth, were often quite tame, bespeaks, once again, evidence of animals that weren't hunted very much, and probably that's a buffer-zone condition that they were finding.